\(x+x\cdot3:\dfrac{2}{9}+x:\dfrac{2}{7}=252\)

\(\Leftrightarrow x+x\cdot3\cdot\dfrac{9}{2}+x\cdot\dfrac{7}{2}=252\)

\(\Leftrightarrow x\cdot18=252\)

hay x=14

\(40+2\left(12-x\right)=60\)

\(2\left(12-x\right)=20\)

\(12-x=10\)

\(x=2\)

\(40+2.\left(12-x\right)=60\)

\(40+24-2x=60\)

\(64-2x=60\)

\(2x=4\)

\(x=2\)

c: \(\Leftrightarrow4^x\cdot15=60\)

hay x=1

1)28.122-28.62+30.144

=28(122-62)+30.144

=28.60+30.144

=30.56+30.144

=30(56+144)

=30.200

=6000

2)52.143-52.39-8.26

=52(143-39)-8.26

=52.104-8.26

=8.676-8.26

=8(676-26)

=8.650

=5200

 Bài 2

a)A\(=\)\(\left(x-3\right)\left(x^2+4\right)-4\left(3-x\right)\)

\(=\left(x-3\right)\left(x^2+4x\right)+4\left(x-3\right)\)

\(=\left(x-3\right)\left(x^2+4x+4\right)\)

\(=\left(x-3\right)\left(x+2\right)^2\)

b)để biểu thức A=0 ⇔ x-3=0 hoặc x+2=0

                                ⇔ x=3  hoặc x=-2 

x(100%+20%)=7.2

x120%=720%

x=720%:120%

x=6

vậy////////

(40%+100%)x+20%=720%

140%x=720%-20%

140%x=700%

x=720%:140%

x=36/7

vậy x=/////////////

x﴾100%+20%﴿

=7.2 x120%

=720% x

=720%:120%

x=6 

Nhưng bn ơiX là x^2 hay tách biệt nếu tách biệt thì là 9/49 còn nếu là x^2 thì là 3/7 nhé

\(=\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{19}-\frac{1}{21}\right)xX=\frac{9}{7} \)\(=\left(\frac{1}{3}-\frac{1}{21}\right)xX=\frac{9}{7}\)\(=\frac{2}{7}xX=\frac{9}{7}\)

\(X=\frac{9}{7}:\frac{2}{7}\)

\(X=\frac{9}{2}\)

ta có:

125⁷⁹=(5³)⁷⁹

625⁶⁰=(5⁴)⁶⁰

=>5³<5⁴ =>(5³)⁷⁹<(5⁴)⁶⁰

=>125⁷⁹<625⁶⁰

lâu rồi ko lm ko bt đúng ko

Ta có: \(125^{79}=\left(5^3\right)^{79}=5^{237}\)

\(625^{60}=\left(5^4\right)^{60}=5^{240}\)

Vì \(5^{237}< 5^{240}\)nên \(125^{79}< 625^{60}\)

\(125^{79}=\left(5^3\right)^{79}=5^{237}\)

\(625^{60}=\left(5^4\right)^{60}=5^{240}\)

mà \(5^{237}< 5^{240}\)

nên \(125^{79}< 625^{60}\)